1. Field of the Invention and Related Art Statement
The present invention relates to an optical record medium such as an optical card and an optical disc, and a method of recording data signals and control signals on the optical record medium.
Conventionally, there has various kinds of optical discs and optical cards are known. In an optical disc of the write once type, since the reliability of a recorded signal is relatively low and the recorded signal could not be erased, it is not suitable to record control data for managing the disc on the disc itself. Therefore, the control data of the optical disc is usually recorded on a separate reliable record medium of the rewritable type such as a floppy disc.
In the optical record medium of the write once type, if the previously recorded information is scarecely referred to, it is not always necessary to rewrite the control data for managing the record medium. In such a case, it is sufficient to record a new control data signal in addition to the previously recorded signal. Such an optical card is disclosed in PCT/US82/00187, and could be used in a prepaid card system. In such a system, it is sufficient to detect a remained amount of money promptly.
FIG. 1 is a schematic view showing the construction of a conventional optical card. In this embodiment, an optical card 1 comprises a data record region 2 in which a plurality of tracks each extending along a card longitudinal direction are parallely arranged in a card width direction. The data record region 2 has an ID region 3 in which track addresses and/or sector addresses are previously recorded, and a data region 4 in which data are to be recorded.
In the optical record medium of the write once type mentioned above, since the data is not rewritten, it is necessary to manage the data by means of the control information representing an attribute of the latest recorded data. Various methods for managing the data by means of the control information have been known as follows.
(1) Record the control information on a rewritable record medium such as a floppy disc in a host computer, and manage the data by means of the control information on the floppy disc. PA0 (2) Record the control information on the optical record medium, read the control information into a RAM in the host computer, manage the data by means of the control information in the RAM and rewrite the latest control information in the RAM, and rewrite the latest control information on the optical record medium in a region different from a region in which the previous control information has been recorded. PA0 a substrate; PA0 a first area provided on the substrate and defining a data region in which a plurality of data tracks for recording a data signal are provided in parallel with each other; PA0 a second area provided on the substrate and defining an identification region in which addresses of said data tracks are recorded; and PA0 a third area provided on the substrate and defining a control data region in which a control data signal for managing the optical record medium is recorded such that a control data signal for a data track is aligned with the relevant data track; whereby the identification region and control data region are extended in a track width direction. PA0 selecting at least one track among said tracks as a control data track; PA0 recording a data signal in a data track which is not selected as the control data track; and PA0 recording a control data signal for managing the optical record medium in the control data track.
FIG. 2 is a schematic view illustrating a prepaid card system using the optical card shown in FIG. 1 and effecting the management of card by means of the first method (1). The optical card 1 is set in a read/write device 5 and a remained amount of money recorded on the card is read out and is sent to a host computer 6. In the host computer 6, an amount of money which is paid at this time is subtracted from the remained amount of money and then the newly calculated amount of money is recorded as a new remained amount of money on the card 1 by means of the read/write device 5. The new remained amount of money is recorded in the data record region 4 at such a position next to a position at which the previous remained amount of money has been recorded.
However, in the method (1) mentioned above, if a large amount of optical record media are to be managed, it is necessary to use a large amount of memories for the control information and thus the system is liable to be expensive in cost. Moreover, if the system is composed as an on-line system, it is necessary to transfer the control information between a plurality of host computers which have to be always remain in an operational condition, and thus, an efficiency of using the optical record medium becomes low. Further, in the off-line system, data recorded on floppy discs has to be exchanged every day, and therefore the host computers could not be spread widely.
Further, in the method (2) mentioned above, since the renewed control information is recorded on the optical record medium at a position next to the previously recorded position, the data record region is decreased every time the control information is renewed. This disadvantage is very serious for the optical card system, because an amount of storage of the optical card is relatively small as compared with that of the optical disc.
In the optical card of the write once type, the data is recorded on successive tracks in the data record region. In such a case, it is necessary to detect the last track on which the latest data has been recorded. In the known method (2), the last track is detected by successively scanning the tracks from the first track. Then, it is apparent that a time period necessary for detecting the last track is liable to be long. General optical cards have a record capacity of up to several MBs and comprise several thousand tracks, so that in an extreme case, several minutes are required until the last track is found.